Prior systems for measuring variable physical parameters typically comprise the following steps: creating a variable reference; comparing the variable reference to the parameter being measured; and varying the magnitude of the reference until it is substantially equal to that of the parameter. Such systems create a digital signal representative of the magnitude of the reference and employ the digital signal in signal processing to create whatever output is desired from the measuring system.
Generally, the step of creating the digital signal requires using a device known as a comparator. A comparator has a bistable output which changes state according to the sign of the difference between two input signals. Unfortunately, the speed with which such a device reacts to a change of the sign of the difference is dependent upon the magnitude of the difference and/or the rate of change of the difference. Further, as a consequence of its bistable operation, comparators exhibit hysteresis. Hysteresis can cause a comparator's measurement to vary according to the direction from which the magnitude of the reference approaches the magnitude of the parameter. These limitations in comparator technology have diminished the accuracy and success of prior measuring systems. Thus, there is a need in the art for a high-accuracy measurement system that compensates for limitations in comparator technology. Further, such a system should operate with low power comparators and be inexpensive as well as simple to operate.